A black farmworker has been found guilty of murdering Eugene Terre'Blanche, the white supremacist whose brutal demise threatened to inflame racial tensions in South Africa.

Chris Mahlangu, 29, was convicted at a court in the small rural town of Ventersdorp. His co-accused, Patrick Ndlovu, 18, was acquitted of murder, but found guilty of housebreaking.

Terre'Blanche, co-founder of the far-right Afrikaner Resistance Movement (AWB), who wanted to overthrow South Africa's black majority government, was killed at his farmhouse in Ventersdorp on 3 April, 2010.

Prosecutors had accused Mahlangu and Ndlovu of breaking into the 69-year-old's home, where they found him asleep, and bludgeoning him to death with a steel pipe. A post-mortem report revealed he sustained 28 injuries.

Mahlangu and Ndlovu pleaded not guilty to murder, housebreaking and robbery with aggravating circumstances. Both declined to testify.

Judge John Horn ruled on Tuesday: "After all the evidence given, I conclude that accused number one is guilty as charged."

Horn dismissed Mahlangu's claim that he acted in self-defence and said there was no evidence that Terre'Blanche was killed due to his political views. The dispute had been over wages on the farm.

While Terre'Blanche was portrayed as arrogant and violent, neither of the accused testified about this, or any claims of abuse, the judge added. "None of these things could justify the brutal attack on the deceased."

His verdict marked the end of a two-year case that had raised fears of a violent backlash along racial lines that would evoke apartheid demons, but ultimately lost its sting to prosaic concerns over legal delays and a botched police investigation.

The AWB organisation waged a bloody and futile campaign to resist the end of white minority rule and the establishment of democracy under Nelson Mandela in 1994. Terre'Blanche, a burly fascist known for his thick white beard, piercing blue eyes and fiery rhetoric, had become an irrelevant figure by the time of his death.

"He was revered by some, but despised by others," Horn said during his judgment.

His body was found on his bed with his underwear pulled down to reveal his genitals. Initial testimony suggested that there was semen on his body, but the substance was never analysed.

Mahlangu claimed that he acted in self-defence after Terre'Blanche had raped him – an allegation that the prosecution said was made up and was rejected by the court. Judge Horn asked why it was only mentioned towards the end of the trial, and only through other witnesses.

He said: "Sodomy is such a personal intrusion, I can't believe [Mahlangu] would not have raised it immediately."

Ndlovu was 15 at the time of the killing and was tried as a minor. The trial has been held behind closed doors to protect his identity. Last month, the judge ruled that most evidence against the teenager was inadmissible because police failed to follow South Africa's child protection law in handling the case.

Terre'Blanche's family said Mahlangu should spend the rest of his life in jail and expressed disappointment at the acquittal of Ndlovu. "He was guilty," relative Andre Nienaber told South Africa's Mail & Guardian. "He was part of it. He admitted it. He should never go free."

During the trial, the defence alleged that the farmworkers had been abused by Terre'Blanche and were trying to defend themselves. A lawyer for Ndlovu said he had been subject to "appalling conditions … not fit for human habitation [and] child exploitation" on the farm."

Terre'Blanche had been jailed in 1997 and sentenced to six years for the attempted murder of a black security guard and assaulting a black petrol-station worker.

After Terre'Blanche's death, some members of the local black community called Mahlangu a hero for his alleged role in the crime. Some Afrikaners claimed his murder highlighted the violence faced by white farmers in South Africa, with around 3,000 said to have been killed since 1994.

On Tuesday, protesters from both sides scuffled outside the courthouse in Ventersdorp, about 80 miles west of Johannesburg. Scores of AWB members wearing military fatigues set up camp with their red, white and black, swastika-style flags planted in the ground.

Nearby, a bigger group of supporters of the two farmworkers sang anti-apartheid songs. Police set up cordons to keep the two sides apart but the tensions did not explode into broader violence, and the crowd showed little reaction to the verdict.

Former AWB leader Andre Visagie said the group would be watching closely what prison sentence Mahlangu now receives.

"We as a people want to see what message the court send out to the farm murderers out there," he told the Mail & Guardian. "Do they spend three or five years in jail, and then get out to murder again? If a firm message is not sent out to the farm murderers, then the rainbow nation will remain a dream."

more on this story

The conviction of a farmworker for the murder of white supremacist leader Eugene Terre'Blanche closes an ugly chapter in South Africa's history. But, explains novelist Christopher Hope, the case has laid bare a bitter anger across the racial divide